1988 Ford Ford Truck

SUMMARY: ZERO BRAKING EFFECTIVENESS, BRAKE PEDAL PRESSURE OKAY, SUDDEN SUSTAINED ABSOLUTE LOSS OF STOPPING ABILITY. YOUR RECALL CAMPAIGN 96V071000 MAY BE MISSING A MECHANISM FOR CATASTROPHIC BRAKE FAILURE ON THE FORD TRUCK. MY 1988 F250HD SUPERCAB 4X4 HAS EXHIBITED THREE DIFFERENT MECHANISMS FOR BRAKE LOSS. WHEN <1 YEAR OLD WITH <10K MILES ON IT, WE DROVE A DIRT ROAD WHICH AFTER LEVEL TRAVEL (I.E. ABSOLUTELY NOT OVERHEATED FROM MOUNTAIN DRIVING) WINDS DOWN A CLIFF. THE HAIRPIN SWITCH-BACKS REQUIRED ME TO JOCKEY THE LONG SUPERCAB AROUND THE CORNERS WITH REPEATED BRAKE APPLICATION, BUT ALL AT NEAR 0 MPH AND OVER ABOUT 15 MINUTES TIME. AT THE BOTTOM OF THE CLIFF @<10MPH TOWARD A CREEK I ATTEMPTED TO SLOW DOWN. THE BRAKE PEDAL STOPPED AT THE NORMAL POINT BUT THERE WAS NO BRAKING FORCE. THERE WAS A DOWNWARD SLOPE (LESS THAN 10 DEGREES PITCH). PUMPING THE BRAKES DID NOT HELP. I PRESSED THE BRAKE PEDAL WITH MAXIMUM FORCE WITH BOTH LEGS! AND COULD NOT EVEN SLOW THE VEHICLE! (THE VEHICLE HAD A FIBERGLASS TOPPER INSTALLED SO PAYLOAD EST. ~1,500 LBS). SUBSTANTIAL FORCE WAS APPLIED TO THE BRAKE PEDAL! IF WE HAD BEEN KILLED, THE BRAKES WOULD HAVE CHECKED OUT FINE AFTER THE FACT. I BELIEVE THERE PROBABLY HAVE BEEN OTHER INSTANCES THAT HAVE GONE UNREPORTED OR WHICH HAVE RESULTED IN ACCIDENTS AND/OR DEATHS IN WHICH THIS BRAKING PROBLEM HAS NOT BEEN IDENTIFIED. BELTS AND BRAKE FLUID WERE NOMINAL. THE FRONT DISKS AND REAR AXLES WERE NOT HOT TO THE TOUCH. MY WIFE APPLIED THE BRAKES WHILE I INSPECTED THE ENGINE COMPARTMENT AND NO ABNORMAL SOUNDS OR OTHER CUES TO THE CAUSE COULD BE OBSERVED. I TURNED THE VEHICLE OFF ANDRESTARTED A COUPLE OF TIMES WITH NO EFFECT. THIS PERSISTED >45 MINUTES WHILE WE TRIED TO DIAGNOSE THE PROBLEM. ON THE UPPER SIDE OF THE BRAKE BOOST CANISTER THERE IS A GROMMET/FITTING FOR THE VACUUM HOSE ATTACHMENT. I ROTATED THIS FITTING TO TENSION THE HOSE FLEXURE IN A DIFFERENT DIRECTION AND THE BRAKES STARTED OPERATING. I HAVE NOT EXPERIENCED A REPEAT OF THE SYMPTOMS.